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Polio Vaccine Switchover: An Untold Success Story In Global Public Health

November 28, 2017

Syed Latif, a polio vaccinator and activist, hands out polio information at the Mansehra Polio Resource Center in Mansehra, Khyber Pakhtunkhwa Province of Pakistan, just north of Abbottabad. Pakistan is down to five cases of polio. Photo: Mansehra Polio Research Center

By David J. Olson

In April 2016, something extraordinary happened in global health. Thousands of community health workers in more than 120 countries — from African villages to the Himalayas to the Pacific Islands — all mobilized and synchronized their efforts to switch from one oral polio vaccine to another. Any slip-ups could have resulted in creating more “vaccine-derived” poliovirus cases at a moment when we are down to our last few cases of polio.

The fact that many children receiving such oral vaccines were living in areas of high conflict and low development (which means low levels of health infrastructure) made the accomplishment all the more remarkable.

The feat was accomplished in a single day (each country was told to pick one day within a two-week period in April 2016 to make the change).

“It was a great achievement, especially when you understand the scope, because it happened in more than 120 countries,” said Joël Calmet, senior director of communication for polio of Sanofi Pasteur, a pharmaceutical company which produces 500 million polio vaccines annually. “I was surprised by two things – the fact that it went well almost everywhere and the fact that no poliovirus type 2 has been detected following the removal of the outdated trivalent oral vaccine.”

The Polio Eradication and Endgame Strategic Plan 2013-2018, approved by the World Health Organization (WHO) in 2013, calls for the removal of all oral polio vaccines (OPVs) by 2019-2020, including the trivalent OPV (which protects against three strains of poliovirus) that was replaced in April 2016 and the bivalent OPV (which protects against two strains) now being used.

Eventually, the bivalent OPV will be replaced by an injectable polio vaccine. Until polio is eradicated, using both injectable and oral vaccines provide the best form of protection, according to the Polio Global Eradication Initiative. But by 2019-2010, the plan is to use only the injectable vaccine.

The obsolete trivalent OPV contained all three poliovirus serotypes (1, 2 and 3) and led to the eradication of wild poliovirus 2 in 1999. The last detected case of wild polio virus 3 was in 2012. Now we are down to the last 15 cases of wild poliovirus 1 and those last few cases are proving the most difficult to eliminate. Even after wild poliovirus 1 is “eliminated,” three more years will be required before WHO can verify that it has been “eradicated.”

When that happens, it will be only the second human disease ever eradicated, after smallpox, which was declared eradicated in 1980. Guinea worm is also close to eradication with the Carter Center reporting only 26 cases reported in 2017 in Chad and Ethiopia.

There are also 80 cases of circulating vaccine-derived polio virus cases – 70 in Syria and 10 in the Democratic Republic of Congo – but these are believed by WHO to be “ancient strains” and not related to the switchover in OPVs, according to Calmet.

Frank Conlon, director of the Core Group Polio Project, recalls the destruction of the poliovirus type 2 in Kenya. “I was one of the honored guests last year at the Kenya Medical Research Institute laboratory to witness the destruction of their final stocks of Type 2 poliovirus that were contained in the laboratory. It was a big event for Kenya, and it was widely attended by the press.”